Background: Previous studies discuss the positive predictive value through whether the bacteria are coagulase-negative staphylococci. The view may need to be updated. The aim was to evaluate the positive predictive value of different bacteria species isolated from cerebrospinal fluid cultures and discuss the rationality to view coagulase-negative staphylococci as a group.
Methods: This retrospective cohort study recruit all adults with positive cerebrospinal fluid cultures sampled by lumbar puncture 2012-2020 in the Department of Neurosurgery. The exposure was bacteria species, and the outcome was positive predictive value. An episode was defined as a patient with one bacteria. When episodes with a bacteria species reached five, the bacteria species was analyzed specifically. The positive predictive value was defined as the incidence of isolated-bacteria-related infected episodes. The isolated-bacteria-related infected episode was defined as the patient was with clinical features of bacterial meningitis, and the improvement was related to sensitive antibacterial agents. Then the differences of the positive predictive value of different bacteria in all specific bacteria species, coagulase-negative staphylococci, and non-coagulase-negative staphylococci bacteria were calculated, respectively. The results were statistically significant when P-value <.05.
Results: 1180 episodes from 1133 patients with 79 bacteria were studied; the positive predictive value was 54.3%. The bacteria included 67 bacteria species, ten bacteria genus, viridans streptococci, and unclassified coagulase-negative staphylococci. Twenty-four specific bacteria species were analyzed. The range of positive predictive values of them was 29.4%-100.0% (P<.0001). The positive predictive value for Enterobacter aerogenes, Pseudomonas aeruginosa, Enterobacter cloacae, and Klebsiella oxytoca was the highest, while the positive predictive value for Staphylococcus cohnii was the lowest. Moreover, 767 (65.0%) were with coagulase-negative staphylococci, the positive predictive value was 46.4%, and the range was 29.4%-85.7% (P=.0020); 413 (35.0%) were with non-coagulase-negative staphylococci bacteria, the positive predictive value was 69.0%, and the range was 40.0%-100.0% (P<.0001).
Conclusions: This study suggests that the positive predictive value of different bacteria species is different. It is more reasonable to discuss the positive predictive value of bacteria isolated from cerebrospinal fluid cultures through the bacteria species rather than whether they are coagulase-negative staphylococci.
Trial registration: This is a retrospective study without interventions on participants.